Re: Very slow transfers to/from micro SD card on a RPi B+

[Reinoud Zandijk <reinoud%NetBSD.org@localhost>]

Hi,

On Thu, Jul 09, 2015 at 11:53:26AM -0400, Michael wrote:
> On Thu, 9 Jul 2015 11:28:17 +0200 Jean-Baka Domelevo Entfellner
> <domelevo%gmail.com@localhost> wrote:
> > I'm currently untarring a pkgsrc.tar.gz (48MB) to /usr. The commandline I
> > used is: # nohup tar xfz pkgsrc.tar.gz -C /usr &
> ...
> > It's on average between 0.20 and 0.25 MB/s, don't you think it's
> > unreasonably slow? Do you have any piece of advice for me?
> 
> It should write at least 1MB/s. Is the partition you're writing to aligned
> to something like 16MB? Really odd alignments ( like, less than a filesystem
> block ) will force the card to do lots and lots of read-modify-write cycles
> which will slow it to a crawl.

This is a common issue with most file systems indeed. I'd advise to use WAPBL
(-olog) or even async (-oasync). Esp. async ought to be a lot faster.

Reminds me that I really ought to put my FS work higher on my TODO list.

Reinoud